1,720,955 research outputs found
Estudio de parámetros físicos de interés en dosimetría de hadrones
Get PDFTesis (Lic. en Física)--Universidad Nacional de Córdoba, Facultad de Matemática, Astronomía y Física, 2013.Fil: Quiroga, Flavia. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina.La radioterapia utiliza radiaciones ionizantes para producir daño en las células con las cuales interactúa. La hadronterapia es la técnica de radioterapia que emplea haces de iones pesados como radiación ionizante. En contraste con la distribución de dosis depositada por fotones y electrones (radioterapia convencional), los iones depositan baja dosis en superficie, presentando un máximo agudo (pico de Bragg) a una determinada profundidad. Luego del pico de Bragg la dosis cae abruptamente. La alta precisión balística y eficacia biológica de este tipo de haces permite concentrar altas dosis en la zona tumoral preservando el tejido sano y órganos vecinos. La
dosimetría de hadrones se basa en la determinación de dosis absorbida en profundidad en agua (principal componente del tejido vivo), a partir del porcentaje de ionización que ocurre cuando el haz atraviesa cámaras de ionización que contienen aire. Tanto la calibración de los equipos como el subsiguiente cálculo de dosis a ser suministrada al paciente dependen de diversos parámetros físicos que intervienen en esta conversión, siendo el cociente de poderes de frenado agua-aire, uno de los
que aporta la mayor fuente de incerteza. En el presente trabajo se realiza un estudio exhaustivo de los modelos teóricos y experimentales del cociente de poderes de frenado agua-aire.Radiotherapy uses ionizing radiation to produce damage in the cells with which it interacts. Hadrontherapy is the radiotherapy technique that uses beams of heavy ions as ionizing radiation. In contrast to the dose distribution deposited by photons and electrons (conventional radiotherapy), the ions deposit a low dose on the surface, presenting a sharp maximum (Bragg peak) at a certain depth. After the Bragg peak the dose drops abruptly. The high ballistic precision and biological efficacy of this type of beam allows high doses to be concentrated in the tumor area while preserving healthy tissue and neighboring organs. The
hadron dosimetry is based on the determination of absorbed dose in depth in water (main component of living tissue), from the percentage of ionization that occurs when the beam passes through ionization chambers containing air. Both the calibration of the equipment and the subsequent calculation of the dose to be delivered to the patient depend on various physical parameters involved in this conversion, with the water-air braking power ratio being one of the most important sources of uncertainty.
one of those that provides the greatest source of uncertainty. In the present work an exhaustive study of the theoretical and experimental models of the water-air stopping power ratio is carried out.Fil: Quiroga, Flavia. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Immobilization of bacteria in microgel grafted onto macroporous polyethylene
Get PDFThe development of "Green Chemistry" requires new materials to replace the conventional organic chemistry by biological catalysts, to produce fine chemicals in an environmentally friendly manner. Microbial whole cells can be directly used as biocatalysts, providing a simple and cheap methodology since enzyme isolation and purification are avoided. High-density polyethylene (HDPE) is a very stable polymer though it can be activated by gamma radiation to induce grafting. Glycidyl methacrylate was grafted onto macroporous HDPE and PP in the range of 1-6%, proportional to the initial monomer concentration. Grafted polymers were further chemically modified with ethylenediamine to generate a cationic hydrogel of micron-size thickness onto the internal polymer surfaces. Modified polymers were able to immobilize Gram-positive and Gram-negative bacteria that can catalyze a chemical reaction as efficient as free cells do.Fil: Trelles, Jorge Abel. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Quiroga, Flavia Yanina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Britos, Claudia Noelia. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Smolko, Eduardo E.. Comisión Nacional de Energía Atómica; ArgentinaFil: Grasselli, Mariano. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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